1. Field of Invention
The present invention relates to an air bag in air bag system installed in an automotive steering wheel and an instrument panel in front of the passenger seat.
The present application is based on Japanese Patent Applications No. Hei. 11-292984 and 2000-070620, which are incorporated herein by reference.
2. Description of the Related Art
There is a known an air bag system installed in a steering wheel as disclosed in JP-A-10-175494, for example, the air bag being folded up and housed in a casing.
More specifically, a peripheral wall portion on a side opposite to an opening for introducing an inflation gas is put on the side of a peripheral wall portion having the opening in such a manner as to set flatly developed peripheral edges closer to the opening side before being folded twice.
The folding at the first stage comprises the steps of forming a lateral crease, and putting the longitudinal edges of flatly developed peripheral edges on a side opposite to an opening under a bellows folding method so that the edges may be set closer to the opening.
The folding at the second stage further comprises the steps of forming a longitudinal crease, and folding the peripheral edges on the two lateral end portions around the opening under an outer roll folding method for winding the peripheral edges so that the edges may be set closer to the opening.
The air bag thus folded up at the two stages is fitted to the bag holder of a casing including the bag holder and an air bag cover (pad). Then the pad is coupled to the bag holder whereby to house the air bag in the casing.
An inflator for supplying an inflation gas to the air bag is simultaneously incorporated in the air bag system when the air bag is housed in the casing to complete the assembly work. Moreover, the air bag system utilizes the casing (bag holder) for being fitted to the steering wheel body coupled to the steering shaft of a vehicle whereby to assemble and mount the air bag system on the vehicle.
In the case of such a conventional air bag, however, the peripheral wall portion on the side opposite to the opening is put on the side of the peripheral wall portion having the opening for introducing the inflation gas to form a flatly developed air bag. Then the air bag is halved and folded up at the first stage and further the laterally long folded regions are again folded up at the second stage. The flatly developed air bag is ultimately folded into two packs and the problem is that finished air bag tends to become thicker.
In order to reduce the thickness of the air bag system as disclosed in JP-A-10-175494, the two packs thus folded up at the second stage have been distributed to the respective spaces on both sides of the inflator for supplying the inflation gas to the air bag.
Notwithstanding, though the distribution of the folded packs to the respective spaces of the inflator may result in reducing the thickness of the air bag, the shape of the folded air bag as viewed from above becomes larger and this makes it difficult to house the air bag in a compact casing.
Moreover, the region where the air bag is folded is disposed in the vicinity of the outer peripheral edge apart from the center of the inflator and the pack of the folded air bag is not disposed between the air bag cover region used to substantially cover the center of the folded air bag and the inflator, so that there existed a space therebetween. When a horn switch is turned on by holding down the air bag cover, the above region of the air bag cover may yield to the pressure in a case where the center of the air bag cover is substantially held down. In other words, the touch of the air bag cover has been bad.
Needless to say, the bad touch above has occurred in not only such an air bag cover for operating the horn switch but also an air bag cover with a horn button provided separately.
An object of the invention intended to solve the foregoing problems is to provide an air bag in an air bag system that can be housed in a compact casing.
Another object of the present invention intended to solve the foregoing problems is to provide an air bag system capable of improving the touch of its air bag cover.
An air bag in an air bag system according to the invention wherein a peripheral wall portion on a side opposite to an opening for introducing an inflation gas is put on the side of a peripheral wall portion having the opening in such a manner as to set flatly developed peripheral edges closer to the opening side before being folded twice whereby to house the air bag in a casing, is characterized in that
the peripheral wall portion on the side opposite to the opening is put on the side of the peripheral wall portion having the opening and flatly developed; the peripheral edges in three directions around the opening are folded together closer to the opening side at the first stage; and the peripheral edges on the end portion side thus folded in the three directions around the opening are folded at the second stage in such a manner as to set the peripheral edges closer to the opening side whereby to house the air bag in the casing.
The folding at the second stage is preferably carried out under an outer roll folding method for winding each of the peripheral edges on the end portion side thus folded at the first stage on the side of the peripheral wall portion having the opening.
In this case, preferably, the casing is disposed in a boss portion in the center of a steering wheel; and the boss portion includes a space on its front portion side with respect to a ring portion to be held when the steering wheel is turned.
Further, the folding at the first stage is preferably carried out under a bellows folding method for folding the peripheral edges in the three directions around the opening on the side of the peripheral wall portion on the side opposite to the opening.
Preferably, further, the casing is disposed in the boss portion in the center of a three-spoke type steering wheel; and only one folded region out of those folded at the second stage is housed in the casing so that the region may be disposed on the front side of the steering wheel.
Further, the casing may be disposed in the boss portion in the center of a steering wheel with an inflator for generating the inflation gas disposed in the base wall portion; and only one folded region out of those folded at the second stage is disposed on the rear side of the inflator, whereas the remaining two folded region out of those folded at the second stage is disposed respectively on the lateral side of the inflator.
Further, the casing preferably has an inflator disposed in the base wall portion; and at least one folded region out of those folded at the second stage is housed in the casing with part of the one folded region being mounted on the inflator.
The air bag according to the invention is such that the peripheral edges in three directions around the opening are folded together closer to the opening side at the first stage where the flatly developed air bag is folded. Then the peripheral edges on the end portion side folded in the three directions around the opening are folded closer to the opening, so that the flatly developed air bag is ultimately folded into three packs by putting the peripheral wall portion opposite to the opening on the side of the peripheral wall portion having the opening for introducing the inflation gas.
In other words, since the air bag according to the invention consists of three folded packs, any one of the packs can be reduced in thickness and shape as viewed from top as compared with the conventional casing where two packs are formed.
Moreover, the three packs that are ultimately folded can easily be disposed radially around the opening. Since each one of the packs thus folded up is smaller in shape than the conventional pack, the air bag in top view after it has been completely folded up can be made smaller.
Therefore, the air bag in the air bag system according to the invention can readily be housed in a compact casing.
Under the outer roll folding method at the second stage, though the region opposite to the opening tries to protrude while canceling the folding of the three packs (folded regions) covering the region opposite thereto during the initial period of air-bag inflation, each pack wound on the side of the peripheral wall portion having the opening is hardly unwound because the pack is wound on the side thereof in comparison with the bellows or inner roll folding method (for folding the folded end portion on the side of the peripheral wall side opposite to the opening). Consequently, any region opposite to the opening is restrained from protruding.
When the folding of the three packs is canceled, the inflation gas is dispersed minutely in the three directions of the three packs, so that the flow rate of the inflation gas for canceling the folding of each of the packs is reduced. In other words, the region opposite to the opening is increasingly suppressed as the rate of cancellation of the folding of each pack is also suppressed.
Therefore, the adoption of the outer roll folding at the second stage makes it possible to prevent the initiation of air-bag inflation even though the air bag tries to interfere with a driver or passenger by lowering the pressure applied to the driver or the like.
When the conventional air bag is inflated, the folding of the two packs is canceled and the inflation gas is only divided in the two directions of these two packs, whereby the flow rate of the inflation gas that cancel the folding of each pack increases, thus accelerating the cancellation of the folding.
When the folding is carried out under the outer roll folding method at the second stage, the casing is disposed in the boss portion in the center of the steering wheel. Further, the provision of the space on the front side of the boss portion with respect to the ring portion gripped when the steering wheel is turned makes it possible for the air bag to escape into the space between the front side of the boss portion and the ring portion even though the air bag interferes with the driver in the proximity of the steering wheel, that is, suppressing the pressure of the air bag applied to the driver. In other words, the air bag causes its region opposite to the opening to protrude while canceling the folding of the three packs in the folded region during the initial period of inflation. As the three packs in the folded region are wound on the side of the peripheral wall portion having the opening, their winding is released in such a manner as to extend outward to move the driver without interfering with the driver when the driver in the proximity of the steering wheel interferes there with. When the ring portion interferes with the driver, the winding of the packs is released in such a way as to move down the ring portion. Consequently, the greater space between the front side of the boss portion and the ring portion allows the packs to enter the lower side of the ring portion, thus preventing the packs from projecting toward the driver side. Needless to say, the region opposite to the opening is as aforementioned restrained from protruding because of the outer roll folding and set the air bag free from interfering with the driver while moving the driver away, whereby the packs in the folding region enter the lower side of the ring portion while releasing their winding.
When the folding is carried out under the bellows folding method at the first stage, further, the crease is successively added from the peripheral edge side, so that the folding of the air bag is facilitated in comparison with the outer or inner roll folding.
With the casing disposed in the center of the three-spoke type steering wheel, only one folded region (pack) at the second stage is housed so that it may be disposed on the front side of the steering wheel, whereby the two folded packs other than what is disposed on the front side of the steering wheel are respectively disposed on the left and right rear sides of the boss portion of the steering wheel in top view. Thus, small folded packs can be disposed laterally and uniformly and in addition, as each of the folded packs is small, the folded air bag can easily be housed in the compact casing of the boss portion in the three-spoke type steering wheel.
In the case of the three-spoke type steering wheel, the spoke portion includes two spokes laterally extending from the boss portion and one spoke extending backward therefrom. The boss portion used to couple these three spokes is desired to be smaller in order to improve external design as well as meter visibility on the rear edge side of the boss portion as compared to that of any four-spoke type steering wheel, and this results in setting the spokes diagonally and linearly closer to the center of the boss portion. Therefore, the casing disposed in such an air bag system has been desired to be as compact as possible.
Further, the casing is disposed in the boss portion in the center of the steering wheel with the inflator for generating the inflation gas disposed in the base wall portion, and only one folded region out of those folded at the second stage is disposed on the rear side of the inflator, whereas the remaining two folded region out of those folded at the second stage is disposed respectively on the lateral side of the inflator, whereby the inflator heavier than the packs in the folded region of the air bag can easily be disposed on the front side of the casing. Moreover, the disposition of the heavy inflator on the front side of the casing allows the center of gravity of the air bag system to be set closer to the rotational center of the front-side steering wheel during its operation. Thus, the center of gravity balance of the steering wheel in operation is made improvable.
When the air bag system is installed in the boss portion of the steering wheel, a large space has been provided between the front side of the boss portion and the ring portion so as to improve the meter visibility. In other words, the center of gravity of the air bag system is situated on the rear side further than the rotational center of the steering wheel in operation.
When the casing having the inflator for generating the inflation gas is disposed in the base wall portion, at least one folded region out of those folded at the second stage is housed in the casing with part of the one folded region being mounted on the inflator whereby to the air bag is ultimately folded into three packs according to the invention. In comparison with the conventional case where the air bag is folded into two packs, one pack can be decreased in thickness and shape in top view and so the thickness of the completely folded air bag system even though part of the folded region is mounted on the surface of the inflator. Accordingly, the shape of the completely folded air bag is also reducible in top view since part of the folded region is mounted on the surface of the inflator, so that the air bag may be housed in a more compact case.
An air bag system according to the invention wherein a flatly developed air bag is folded substantially closer to the center of the air bag and contained in an air bag cover and wherein
the region of the air bag cover which is positioned above and substantially closer to the center of the air bag thus folded up is thick-walled so that the region thereof may protrude downward from the periphery of the air bag.
The air bag system wherein after the air bag is flatly developed with its peripheral wall portion which has an opening for introducing an inflation gas and is placed on top of a peripheral wall portion on the side opposite to the opening is preferably such that peripheral edges in three directions around the opening are folded so as to be set closer to the opening at a first stage, and the peripheral edges on the sides of end portions thus folded in the three directions around the opening are folded again so as to be set closer to the opening at a second stage whereby to have the air bag contained in a casing.
As the region of the air bag cover which is positioned above and substantially closer to the center of the air bag thus folded up is thick-walled so that the region thereof may protrude downward from the periphery of the air bag, the thick-walled region is allowed to enter the pack-to-pack space of the folded air bag. Consequently, even though the region is held down, the thick-walled portion is supported by part of the air bag with the effect of preventing the air bag cover from being.
In the air bag system according to the invention, the touch of the air bag cover is improvable.
Further, the air bag is finally folded into three packs after the air bag is flatly developed with its peripheral wall portion which has an opening for introducing an inflation gas and is placed on top of a peripheral wall portion on the side opposite to the opening.
In comparison with the conventional arrangement of folding an air bag into two packs, the air bag of the invention folded into three packs is able to decrease the thickness and shape of one pack in plan view. Therefore, the thickness of the completed air bag after assembly is reducible.
Moreover, the air bag according to the invention has ultimately three folded packs radially around the opening with each folded pack being by far smaller than the conventional one, so that the air bag in plan view can be made smaller.
In the air bag system as claimed in claim 2 according to the invention, the air bag can readily be contained in a compact casing.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.